Actually, it’s this islet in the upper left here, seen with North Farallon Island and St. James Island in the lower right. (I’m surprised that this unnamed rock hasn’t yet been named for a longtime local political strongman like Willie Brown or Rose Pak):

CHP Oakland:“Not something you see everyday… It took three CHP vehicles to safely stop traffic and get this bicyclist out of the center divider on I-80 near the MacArthur maze today. If you see something suspicious call 911 and be sure to give us a location , direction of travel and information on what you see! It may just save a life!”

But then check out these fun facts, and the video below, which shows how rat-like it is.

-Muskrats are large rodents that always live near water. They have thick brown fur and a long, furless, scaly tail. They can grow up to two feet long (with tail). Their rear feet are webbed for swimming, and their eyes and ears are very small.

-Muskrats live in marshes, or alongside ponds, lakes, rivers, and streams.